Field of the Invention
The present invention relates to an image holding member, particularly to an image holding member having superior potential characteristics.
Image holding members are generally used as electrophotographic photosensitive members, electrostatic image-and/or toner-image-holding members such as intermediate transfer members or electrostatic recording members, in which many times of image transfer is required, printing plates, and the like.
In the aforementioned electrophotographic photosensitive members which are basically constituted of an electroconductive substrate and a photosensitive layer, a subbing layer provided between the electroconductive substrate and the photosensitive layer is known to be effective in improvement of adhesiveness of the photosensitive layer to the substrate, improvement of coating characteristics of the photosensitive layer, protection of the electroconductive substrate, coating of the defects of the electroconductive substrate, protection of the photosensitive layer against electrical damage, improvement of charge-injection from the electroconductive substrate to the photosensitive layer, and other purposes.
Known materials for the subbing layer include polyvinyl alcohol, polyvinyl methyl ether, poly-N-vinylimidazole, ethylcellulose, methylcellulose, ethylene-acrylate copolymers, casein, gelatin, polyamides, and the like.
As a characteristic required for the subbing layer is mainly named an electric property. As used in an electrophotographic photosensitive member, the subbing layer should not adversely affect the electrophotographic characteristics of the photosensitive member. Accordingly, the electric resistance thereof is required to be low. In positive development, a high electric resistance of the subbing layer causes the voltage on electrification to be applied to the subbing layer, resulting in a high residual potential to cause fogging of the image, while in reversal development, it lowers the image density. Additionally, the electric resistance is required not to be adversely affected by variation of external environment, especially by variation of atmospheric humidity: a low humidity, for example, raises the electric resistance.
In order to achieve the high contrast of the image, the surface potential is required to be as high as possible and the light portion potential to be as low as possible.
In image holding members other than the electrophotographic photosensitive member, for example, in an electrostatic recording member having an electroconductive substrate and a dielectric layer, an intermediate layer provided between a substrate and a dielectric layer is also required to have similar characteristics.
Accordingly, an extremely thin resin layer, and a dispersion of a metal or a metal oxide as a particulate electroconductive material are proposed for this purpose (Japanese Patent Application Laid-open No. 59-84257, and No. 58-181054). The present invention provides a subbing layer having still better characteristics.